Couldn't find much, just two descriptions.
"A hybrid craft, half sail and half oared. Long and narrow. Could
carry up to 50 guns. Able to operate in calm weather. Galley slaves
were chained to the benches." -
Shipwreck database
"On the same day, another Spanish ship, the Zuniga, appeared off Liscannor. This was one of the four galleasses which sailed with the Armada, a long narrow ship, powered both by oars and a large square sail."
"4 galleasses, displacing about 1000 tons each"
It seems that the Spanish galleass used a square sail, as opposed to the 'traditional' triangular ones

. It also says they had the ability to 'tow' ships, but I don't imagine that would help you, or would even be unique to these ships in particular.
I also came across a site referring to it as a "flag galleass", but I couldn't tell you what that means.
If your using\need this for what I think you need it for, then I think a surrender animation might be cool.
I can't tell you the color, but from the pic above it seems to be made of a darker, more polished wood. You may want to check the
Ulster Museum